1. Field of the Invention
The present invention relates to a fiber manufacturing method, a non-woven fabric manufacturing method, and fiber manufacturing equipment.
2. Description Related to the Prior Art
Cellulosic materials are currently attracting attention as biomass materials capable of being recycled by photosynthesis and as materials capable of being biodegraded in the environment. Non-woven fabrics made of cellulose triacetate that is one cellulosic material can be widely used for disposable diapers, masks, various filters, osmosis membranes, reverse osmosis membranes, moisture-permeable sheets, waterproof sheets, and the like.
As a non-woven fabric manufacturing method, for example, Japanese Patent Publication No. 3789006 (corresponding to United States Patent Publication No. 6248267) suggests a method of manufacturing discontinuous fibrillated fibers using a spinning nozzle having a polymer supply port, a coagulant supply port, and a mixing cell unit. In this manufacturing method, a polymer solution is supplied to the polymer supply port, steam is supplied to the coagulating material supply port, and the polymer solution is mixed with steam in the mixing cell unit and is coagulated. Additionally, Japanese Patent Publication No. 2821991 suggests cellulose acetate fibers assuming a fiber surface form having fine projections in a direction substantially perpendicular to a fiber axis in order to improve a dry feeling and color development properties. Moreover, Japanese Patent Application Publication No. 2012-77388 suggests a non-woven fabric manufacturing method of manufacturing a cellulose type non-woven fabric that has excellent mechanical physical properties, rigidity under high temperatures, and water absorptivity, using a method with a low environmental burden.
In the related-art non-woven fabric manufacturing methods, as described in Japanese Patent Publication No. 3789006, an acetone solution of cellulose diacetate is fibrillated by using steam as a coagulant. Additionally, as described in Japanese Patent Publication No. 2821991, for example, dry fiber spinning is performed using a methylene chloride or methanol solution of cellulose triacetate. However, in all of the above methods, it is necessary to recover or render harmless solvent gas that is generated in manufacturing processes because a solvent, such as acetone, methylene chloride, or methanol, is used as the solvent. For this reason, there is a problem that large-scale equipment and considerable energy are required for the recovery or rendering harmless. Accordingly, in the related art, in order to avoid mass processing of the solvent gas, small-quantity production is performed with small-scale production equipment, and the volume of a non-woven fabric obtained becomes small. Additionally, Japanese Patent Application Publication No. 2012-77388 discloses a melt-spinning method that does not use a solvent, and is one of solutions to the above problems. However, in order to obtain ultrafine fibers, a solution method using volumetric shrinkage accompanying solvent evaporation is excellent.